Subclass Variants
The subclasses found in officially published materials cover a wide variety of character fantasies. But, there are cases where the existing material provides a subclass that just narrowly does not fulfill a particular character fantasy that the flavor of the subclass could point to.
This isn't to say those subclasses are broken or unsatisfactory, but rather that there exists a design space where subclasses could be tweaked just a bit to cover a more comprehensive array of fantasies. That is, by modifying or replacing a feature as an alternative to designing a whole new class or subclass.
Presented here are three such variants of existing subclasses: a variant Eldritch Knight, a variant Arcane Trickster, and a variant Draconic Bloodline.
Variant Eldritch Knight
When a fighter takes the Eldritch Knight martial archetype, they can choose to take the following variant feature to modify what spells of 1st-level and higher the Eldritch Knight can learn. Once an Eldritch Knight has decided to take this variant feature or not, they can not change their decision.
Spell Blade
All wizard spells of 1st-level and higher you learn as an Eldritch Knight must be chosen from the abjuration and evocation spells on the wizard spell list, without exception. Additionally, the following spells are added to the wizard spell list for you: Searing Smite, Thunderous Smite, Wrathful Smite, Branding Smite, Blinding Smite, Staggering Smite.
Variant Arcane Trickster
When a rogue take the Arcane Trickster roguish archetype, they can choose to take the following variant feature to augment their magical attacks with their roguish talent of finding weak spots, rather than magically augmenting their larcenous talents.
Arcane Precision
Starting at 3rd level, you gain an additional way to use Sneak Attack. When you hit with a spell attack that uses your Intelligence as its spellcasting ability, you can Sneak Attack as if you were using a finesse or ranged weapon. All the other rules for Sneak Attack still apply.
This feature replaces Mage Hand Legerdemain.
Variant Draconic Bloodline
When a sorcerer of the Draconic Bloodline sorcerous origin reaches level 6, they can choose to take the following variant feature to manifest the growth of their power physically at the expense of comparatively less powerful elemental magic.
Dragon Disciple
At 6th level, you've developed your draconic bloodline for martial combat. You can shift your hands into draconic claws, which last until you shift your hands back to normal. Shifting your hands in this way requires no action. Your draconic claws are magical natural weapons, which you can use to make unarmed strikes. If you hit with them, you deal slashing damage equal to 1d6 + your Strength modifier, instead of the bludgeoning damage normal for an unarmed strike.
You can attack with your draconic claws twice, instead of once, whenever you take the Attack action on your turn.
This feature replaces Elemental Affinity.